The present invention relates to connectivity between land-based cellular communications systems and user equipment located in air-borne craft.
The world is becoming more and more connected, and this has led consumers to have increasing expectations of being able to be online and experience at least moderate data rates regardless of time and location. As one response to these expectations, the next generation of mobile technology, the so-called IMT-2020 (5G), targets high-speed mobility as one objective. The exemplary scenarios studied are high-speed trains and vehicles on freeways, but following the recent trend, it is expected that terrestrial in-flight broadband service for airplanes will be in the scope—either as direct communication between the User Equipment (UE) and base station, or via an access point (AP) onboard the aircraft which aggregates the traffic of some number of UEs and maintains a link to the base station.
In 2013 the Federal Communications Commission (FCC) took steps towards enabling better connectivity by assigning a 500 MHz wide subband in the 14 GHz radiofrequency (RF) band for in-flight air-to-ground broadband connection. The FCC's expectation is that by year 2021 there will be a demand for 15000 flights offering high-speed broadband connectivity to its passengers. By comparison, the availability in year 2013 was 3000 airplanes world-wide, and this was with connections that were deemed too slow and by far too expensive by consumers. The industry has noted that today's airline passengers expect the same level of broadband service that is available on the ground.
Several trials have been carried out offering terrestrial network coverage in lower frequency bands typically used for regular cellular networks. Recent advances on the regulatory side of aviation will, if properly exploited, greatly enhance and simplify in-flight broadband services that are based on terrestrial networks.
The two main systems in use today for air-to-ground communications are:                Aircraft Communications Addressing and Reporting System (ACARS), and        Future Air Navigation System (FANS),        
Of the two, FANS is the more modern and will replace ACARS, offering, for example, Internet Protocol (IP)-based air traffic controller-pilot data link communication (CPDLC) over the Aeronautical Telecommunications Network (ATN).
The air-to-ground communication is either towards a ground station or, in the absence of coverage, a satellite.
Conventional technology exists for providing aircraft-borne devices access to terrestrial radio systems. For example, U.S. Pat. No. 8,914,022B2 discloses directing RF beams towards an aircraft to provide a terrestrial unidirectional or bidirectional broadband data link in parallel with the existing ACARS link. Moreover, depending on whether the data transfers are heavy on the uplink or the downlink, one can split the uplink and downlink radio spectrum resources proportionally to the load. In case there is more than one data link served by an RF beam, of which there may be several in a cell, the radio resources can be arbitrated and shared using time-division multiplexing (TDM). It is however required that there already be a bidirectional ACARS link (short message link) over which the establishment of the parallel data link can be initiated.
There are drawbacks associated with the technology described by U.S. Pat. No. 8,914,022B2. For example, the terrestrial network operator has to rely on an ACARS communication link operated by a third party. Likely, the terrestrial network operator also has to rely on positioning information at least initially provided by the same third party, before the same information can be conveyed over the terrestrial network operator's link; otherwise beams will have to be active in all directions all the time to allow airplanes entering the coverage to identify the network and carry out random access.
Taking another example, U.S. Pat. No. 9,008,669B2 teaches that one can use adaptive beamforming in a terrestrial radio access network so that coverage tracks airplane movement. Moreover, it is taught that for the purpose of estimating and compensating for Doppler shifts, one may, onboard the airplane, provide GPS information or positioning information from the navigation system to the wireless communication device, which may additionally convey such information to the ground station.
There are drawbacks associated with the technology described in U.S. Pat. No. 9,008,669B2. For example, it is proposed that information about position, altitude and speed is to be provided by the wireless communication device to the base station on the ground. But a problem is that before the link has been established, no such information can be conveyed. Either the terrestrial network operator has to rely on a third party, at least for initial positioning of the airplane, or else beams will have to be active in all directions all the time to allow airplanes entering the coverage to identify the network and carry out random access.
Conventional technology therefore suffers from at least the following problems:                Involving a third party complicates the business model for the terrestrial operator, and may incur unnecessary expenses such as payment per established link or received positioning information. The third party may also refuse to provide the service requested by the terrestrial network operator.        Always providing coverage in all directions to allow airplanes entering the coverage area to identify the terrestrial network and to carry out random access is energy inefficient.        
Hence there is a need for technology by which the terrestrial network operator does not depend on a third party. There is a further need for technology in which beams are transmitting only towards existing airplanes. There is a still further need to provide cellular communication service to airborne transceiver equipment in a manner that provides seamless coverage over a wide geographic area without requiring the transceiver equipment to perform any special operations to accommodate for its velocity and airborne position.